Document storage assemblies forming a compartment (e.g., a currency cassette) and usable with an automated transaction machine often include a platform, such as a pressure plate, to support a stack of bills. The pressure plate, along with any previously stacked bills, can be moved to permit stacking newly received bills. As the number of bills in the stack increases, any slight variation between the plane of the pressure plate and the plane of the stacked bills during movement due to stacking may cause the stack to buckle or drop under the force of gravity. If the stack buckles, the document storage cassette may be unable to accept any more bills for storage and thus the automatic transaction machine may require servicing. It is therefore important to minimize the variation between the plane of the pressure plate with respect to the plane of the stacked bills while stacking newly received bills. It is also important to maximize the space within the document storage cassette that is available for storing currency.
Pressure plate assemblies typically use one or more springs (e.g., conical springs) to bias the pressure plate in a certain direction. In a conventional assembly, the pressure plate uses a pin on each longitudinal edge, which fits into a slot of the storage compartment of the document storage assembly, to guide the pressure plate along a slot while newly received bills are stacked. Other pressure plate assemblies use a cantilever plate that is connected to a sleeve bearing that moves along a post to guide the pressure plate in order to stack newly received bills. Alternatively, a scissor mechanism coupled beneath the pressure plate may be used to move the pressure plate while stacking newly received bills. Yet a further alternative is to configure the pressure plate assembly so as to form a rack and meshed gear arrangement as disclosed in U.S. Patent Publication No. 2004/0195758, which is herein incorporated by reference in its entirety.
In certain arrangements, the document storage assembly is coupled to a bill validator and configured to stack bills within the assembly in a vertical orientation. More specifically, the bills are stacked so that the plane of the stacked bills is oriented in the vertical sense. When such a configuration is required, a condition can arise in which additional force is needed to displace the stack of bills within the document storage assembly. As the stack of bills stored within the document storage assembly increases, the stack begins to fall downward due to the effect of gravity and the stack begins to buckle. As the stack buckles, the frictional force caused by dragging the stack along the interior walls of the document storage assembly greatly increases the force needed to displace the stack of bills during a stacking event of a newly received bill.